Methods and conduits for flowing blood from a heart chamber to a blood vessel

ABSTRACT

Disclosed is a conduit that provides a bypass around an occlusion or stenosis in a coronary artery. The conduit is a tube adapted to be positioned in the heart wall to provide a passage for blood to flow between a heart chamber and a coronary artery, at a site distal to the occlusion or stenosis. The conduit has a section of blood vessel attached to its interior lumen which preferably includes at least one naturally occurring one-way valve positioned therein. The valve prevents the backflow of blood from the coronary artery into the heart chamber.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application Ser.No. 60/099,719, filed Sep. 10, 1998.

FIELD OF THE INVENTION

This invention relates to apparatus and method for implanting a conduitto allow communication of fluids from one portion of a patient's body toanother; and, more particularly, to a blood flow conduit to allowcommunication from a heart chamber to a vessel or vice versa, and/orvessel to vessel. Even more particularly, the invention relates to aleft ventricular conduit and related conduit configurations having ablood vessel graft incorporated therein for controlling the flow ofblood through the conduit to achieve bypass of an occluded or stenosedcoronary artery.

BACKGROUND OF THE INVENTION

Coronary artery disease is a major problem in the U.S. and throughoutthe world. Coronary arteries as well as other blood vessels frequentlybecome clogged with plaque which, at the very least, can reduce bloodand oxygen flow to the heart muscle (myocardium), and may impair theefficiency of the heart's pumping action, and can lead to heart attack(myocardial infarction) and death. In some cases, these coronaryarteries can be unblocked through noninvasive techniques such as balloonangioplasty. In more difficult cases, a surgical bypass of the blockedvessel is necessary.

In a coronary bypass operation, one or more venous segments are insertedbetween the aorta and the coronary artery, or, alternatively, the distalend of an internal mammary artery is anastomosed to the coronary arteryat a site distal to the stenosis or occlusion. The inserted venoussegments or transplants act as a bypass of the blocked portion of thecoronary artery and thus provide for a free or unobstructed flow ofblood to the heart. More than 500,000 bypass procedures are performed inthe U.S. every year.

Such coronary artery bypass graft (CABG) surgery, however, is a veryintrusive procedure which is expensive, time-consuming, and traumatic tothe patient. The operation requires an incision through the patient'ssternum (sternotomy), and that the patient be placed on a heart-lungbypass pump so that the heart can be operated on while not beating. Asaphenous vein graft is harvested from the patients leg, another highlyinvasive procedure, and a delicate surgical procedure is required topiece the bypass graft to the coronary artery (anastomosis). Hospitalstays subsequent to the surgery and convalescence are prolonged.Furthermore, many patients are poor surgical candidates due to otherconcomitant illnesses.

As mentioned above, another conventional treatment is percutaneoustransluminal coronary angioplasty (PTCA) or other types of angioplasty.However, such vascular treatments are not always indicated due to thetype or location of the blockage or stenosis, or due to the risk ofemboli.

Thus, there is a need for an improved coronary bypass system which isless traumatic to the patient.

SUMMARY OF THE INVENTION

The present invention addresses the need in the previous technology byproviding a coronary bypass system which avoids a sternotomy and otherintrusive aspects associated with coronary bypass surgery. It also freesthe surgeon from having to perform multiple anastomoses, as is necessaryin the current process.

The present device provides a conduit for diverting blood directly froma heart chamber, such as the left ventricle of the heart, to thecoronary artery distal to the blockage or stenosis, thereby bypassingthe blocked portion of the vessel. The conduit comprises a tube adaptedto be positioned in the heart wall and having a section of blood vesselattached to the interior of the conduit, to provide a passage for bloodflow which is similar to the body's own blood vessels.

The conduit device is delivered through the coronary artery to aposition distal the blockage or stenosis. At that position, the coronaryartery and the wall of the left ventricle, including the myocardium, arepierced to provide an opening or channel completely through from thecoronary artery to the left ventricle of the heart. The conduit is thenpositioned in the opening to provide a permanent passage for blood toflow between the left ventricle of the heart and the coronary artery,distal to the blockage or stenosis.

The conduit is sized so that one open end is positioned within thecoronary artery, while the other open end is positioned in the leftventricle. Prior to implantation of the conduit, a section of vein orother blood vessel is obtained from the patient, from another humandonor, or from a nonhuman animal. The vein or other blood vessel issized so as to fit within the interior of the conduit. The hollow lumenof the conduit with the blood vessel graft inserted therein provides apassage for the flow of blood.

If desired, the section of blood vessel inserted into the conduit mayinclude one or more naturally occurring one-way valves. The valveprevents the backflow of blood from the myocardium into the leftventricle. For example, a section of vein having a valve therein can beused. Alternatively, the pulmonic valve or aortic valve obtained from anonhuman animal, such as a fetal pig or piglet, can be used to provide aone-way passage for the flow of blood through the conduit.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic, cross-sectional view of a human heart, showing aconduit in the myocardium of the heart for forming a bypass between theleft ventricle and a coronary artery;

FIG. 1B is an enlarged view of the bypass conduit of FIG. 1A;

FIG. 2 is an exploded view of a vein graft incorporated into a heartconduit in accordance with the preferred arrangement;

FIG. 3 is a close-up, cross-sectional view of a blockage or stenosis inthe coronary artery, illustrating the conduit of the preferredarrangement positioned so as to bypass the blockage or stenosis.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

As is well known, the coronary artery branches off the aorta and ispositioned along the external surface of the heart wall. Oxygenatedblood that has returned from the lungs to the heart then flows from theheart to the aorta. Some blood in the aorta flows into the coronaryarteries, and the remainder of blood in the aorta flows on to the restof the body. The coronary arteries are the primary blood supply to theheart muscle and are thus critical to life. In some individuals,atherosclerotic plaque, aggregated platelets, and/or thrombi build upwithin the coronary artery, blocking the free flow of blood and causingcomplications ranging from mild angina to heart attack and death. Thepresence of coronary vasospasm, also known as “variant angina” or“Prinzmetal's angina,” compounds this problem in many patients.

As used herein, the term “heart chamber” primarily refers to theinterior, or lumenal, aspect of the left or right ventricle or the leftor right atrium. The term “conduit,” “stent,” and “tube” herein refer tophysical structures, preferably primarily artificial, that can bepositioned between two or more chambers or vessels, to allow blood flowfrom one chamber or vessel to another. A “shunt” is any natural orartificial passage between natural channels, such as heart chambers orblood vessels. The conduit in the preferred arrangement can be made of avariety of materials, including various metals, such as nitinol, orplastics.

As used herein, the term “heart wall” comprises any one or more of thefollowing portions or layers of the mammalian heart: the epicardium,myocardium, endocardium, pericardium, interatrial septum, andinterventricular septum.

The principles of the present invention are not limited to leftventricular conduits, and include conduits for communicating bodilyfluids from any space within a patient to another space within apatient, including any mammal. Furthermore, such fluid communicationthrough the conduits is not limited to any particular direction of flowand can be antegrade or retrograde with respect to the normal flow offluid. Moreover, the conduits may communicate between a bodily space anda vessel or from one vessel to another vessel (such as an artery to avein or vice versa). Moreover, the conduits can reside in a singlebodily space so as to communicate fluids from one portion of the spaceto another. For example, the conduits can be used to achieve a bypasswithin a single vessel, such as communicating blood from a proximalportion of an occluded coronary artery to a more distal portion of thatsame coronary artery.

In addition, the conduits and related methods can preferably traversevarious intermediate destinations and are not limited to any particularflow sequence. For example, in one preferred embodiment of the presentinvention, the conduit communicates from the left ventricle, through themyocardium, into the pericardial space, and then into the coronaryartery. However, other preferred embodiments are disclosed, includingdirect transmyocardial communication from a left ventricle, through themyocardium and into the coronary artery. Thus, as emphasized above, theterm “transmyocardial” should not be narrowly construed in connectionwith the preferred fluid communication conduits, and other nonmyocardialand even noncardiac fluid communication are preferred as well. Withrespect to the walls of the heart (and more specifically the term “heartwall”), the preferred conduits and related methods are capable of fluidcommunication through all such walls including, without limitation, thepericardium, epicardium, myocardium, endocardium, septum, etc.

The bypass which is achieved with certain preferred embodiments andrelated methods is not limited to a complete bypass of bodily fluidflow, but can also include a partial bypass which advantageouslysupplements the normal bodily blood flow. Moreover, the obstructionsthat are bypassed may be of a partial or complete nature, and thereforethe terminology “bypass” or “occlusion” should not be construed to belimited to a complete bypass or a complete occlusion but can includepartial bypass and partial occlusion as described.

The preferred conduits and related methods disclosed herein can alsoprovide complete passages or partial passages through bodily tissues. Inthis regard, the conduits can comprise stents, shunts, or the like, andtherefore provide a passageway or opening for bodily fluid such asblood. Moreover, the conduits are not necessarily stented or lined witha device but can comprise mere tunnels or openings formed in the tissuesof the patient.

The conduits of the present invention preferably comprise both integralor one-piece conduits as well as plural sections joined together to forma continuous conduit. The present conduits can be deployed in a varietyof methods consistent with sound medical practice including vascular orsurgical deliveries, including minimally invasive techniques. Forexample, various preferred embodiments of delivery rods and associatedmethods are disclosed. In one embodiment, the delivery rod is solid andtrocar-like. It may be rigid or semi-rigid and capable of penetratingthe tissues of the patient and thereby form the conduit, in whole or inpart, for purposes of fluid communication. In other preferredembodiments, the delivery rods may be hollow so as to form the conduitsthemselves (e.g., the conduits are preferably self-implanting orself-inserting) or have a conduit mounted thereon (e.g., the deliveryrod is preferably withdrawn leaving the conduit installed). Thus, thepreferred conduit device and method for installation is preferablydetermined by appropriate patient indications in accordance with soundmedical practices.

In order to restore the flow of oxygenated blood through the coronaryartery, the preferred arrangement provides for the shunting of blooddirectly from the heart to a site in the coronary artery which is distalthe blockage or stenosis.

Although the specification herein will describe the conduit primarilywith reference to the left ventricle, the preferred arrangement can beused with any of the four heart chambers, and with any coronary artery,including the left main coronary artery, the right coronary artery, theleft anterior descending artery, the left circumflex artery, theposterior descending artery, the obtuse marginal branch or a diagonalbranch.

A tunnel or opening is formed through the wall of the coronary arteryand the myocardium and into the left ventricle of the heart which liesbeneath, or deep to, the coronary artery. A conduit is positioned in theopening to keep it open.

The conduit may be introduced into the myocardium in a variety of ways,including by a catheter threaded through the femoral artery into theaorta and thence into the left ventricle and, if necessary, the leftatrium; or by a catheter threaded through the femoral vein into theinferior vena cava and thence into the right atrium and right ventricle.Alternatively, the conduit may be introduced through a surgical incisionin chest wall (thoracotomy) or sternum (sternotomy).

Further details regarding conduits and conduit delivery systems aredescribed in copending patent applications entitled DELIVERY METHODS FORLEFT VENTRICULAR CONDUIT [Attorney Docket No. PERCAR.003CP1], DESIGNSFOR LEFT VENTRICULAR CONDUIT [Attorney Docket No. PERCAR.013A], VALVEDESIGNS FOR LEFT VENTRICULAR CONDUIT [Attorney Docket No. PERCAR.006A],LEFT VENTRICULAR CONDUITS TO CORONARY ARTERIES AND METHODS FOR CORONARYBYPASS [Attorney Docket No. PERCAR.033CP1], and BLOOD FLOW CONDUITDELIVERY SYSTEM AND METHOD OF USE [Attorney Docket No. PERCAR.040A],filed on the same day as the present application, and U.S. Pat. Nos.5,429,144 and 5,662,124, the disclosures of which are all herebyincorporated by reference in their entirety.

The opening through the heart wall (including endocardium, myocardium,and epicardium) and coronary artery can be formed in a variety of ways,including by knife or scalpel, electrocautery, cryoablation,radiofrequency ablation, ultrasonic ablation, and the like. Othermethods will be apparent to those of ordinary skill in the art.

The conduit is provided with a section of vein or other blood vesselpositioned within its interior lumen. The section of vein or other bloodvessel is obtained from the patient, from a donor, or from an animal.Prior to implantation of the conduit, a segment of blood vessel sized tofit with the lumen of the conduit is inserted into the conduit. Theconduit with the graft therein provides a passage for the flow of bloodwhich is similar to the natural human blood vessels. The segment of veinor other blood vessel harvested to fit within the conduit may includeone or more of the valves which naturally occur in the human body. Thesevalves act to prevent the backflow of blood. In the conduit, thesenaturally occurring venous valves prevent the blood from flowing backinto the left ventricle of the heart from the coronary artery. Thesegment of vein is preferably inserted into the conduit prior to theconduit's deployment into the human body by any of various surgical orcatheter-guided techniques known to those of skill in the art.

Referring now to FIGS. 1A and 1B, a coronary artery bypass isaccomplished by disposing a conduit 12 (FIG. 1B) in a heart wall ormyocardium MYO of a patient's heart PH (FIG. 1A). The conduit 12preferably extends from the left ventricle LV of heart PH to a cloggedcoronary artery CA at a point downstream of a blockage BL to create apassageway 8 therethrough. Conduit 12 is preferably made of abiocompatible material such as stainless steel or nitinol, althoughother materials such as Ti, Ti alloys, Ni alloys, Co alloys andbiocompatible polymers may also be used. In one embodiment, conduit 12has a one way valve 6 to allow blood to flow from the left ventricle LVto the coronary artery CA. Although the conduit 12 may elasticallydeform under the contractive pressure of the heart muscle duringsystole, the stent remains open to allow blood to pass from thepatient's left ventricle LV into the coronary artery CA. Duringdiastole, the blood pumped into coronary artery through passageway 8 isblocked by one-way valve 6 from returning to left ventricle LV.

As shown in FIG. 2, a preferred embodiment involves the use of a veingraft 10 taken from the patient. Prior to preparing the conduit 12 forplacement in the patient, a section of vein 10 is obtained from thepatient (i.e., an autologous graft or autograft). Of course, a bloodvessel taken from another human donor (i.e., an allogeneic graft orallograft) or nonhuman animal species (i.e., a heterologous graft orxenograft) could also be used. The vein 10 is preferably taken from thesaphenous vein in the leg of the patient. Alternatively, a donor veincould be used, or a fetal pig or piglet can be obtained and dissected toremove a section of the pulmonary artery having a pulmonic valvetherein, or a section of the aorta having an aortic valve therein, or asimilar vessel having a naturally occurring valve system. In otherembodiments, the endothelial lining of a vein and/or a valve may begrown from one or more tissue cultures, utilizing cloning of donor celllines or other genetic engineering techniques (or “tissue engineering”)known to those of skill in the art. Thus, as used herein, “a section ofblood vessel” may include one or more of the following: a surgicallyresected segment of a blood vessel, with or without one or more valves;the endothelial lining of a blood vessel, taken from an in vitro or invivo specimen; and one or more venous valves, taken from in vitro or invivo specimens.

As noted above, the section of vein 10 or other blood vessel harvestedpreferably contains one or more valves 14, which occur naturally in theveins. The section of vein 10 may also not have a valve. The veinsection 10 is sized so as to be the same length as the conduit 12. Thevein section 10 is placed within the interior lumen of the conduit 12and attached to the inside of the conduit 12 by suturing or otherattachment methods. The natural vein graft 10 is biocompatible andtherefore reduces problems associated with rejection of the conduit 12and clotting around or in the conduit 12. In addition, the vein 10provides a natural valve system 14 that is already used throughout thehuman body to prevent the backflow of blood. In the case of a xenograft,treatment of the graft with chemicals, such as glutaraldehyde, may beundertaken to remove living cells, including antigenic materials, fromthe connective tissue framework of the graft so as to reducethrombogenicity and antigenicity.

Referring now to FIG. 3, a self-expanding conduit 12 having a section ofvein 10 therein is introduced into the wall of the myocardium MYO asfollows. A conduit delivery catheter (not shown), having the compressedconduit 12 mounted on its distal end, is advanced over a puncturemechanism and into the wall of the myocardium MYO at a site distal tothe blockage or stenosis BL in the coronary artery CA. When the conduit12 is properly seated in the myocardial wall MYO, its retaining sheathis withdrawn, allowing the conduit 12 to expand and open a passageway,or maintain patency of the passageway, from the left ventricle of theheart LV to the coronary artery CA. This allows oxygenated blood to flowdirectly from the left ventricle of the heart LV through the conduit 12and to the coronary artery CA, bypassing the section of coronary arteryCA that is blocked BL, as shown by the arrows in FIG. 3.

The conduit 12 may include attachment mechanisms not limited to hooks,barbs, large collars, and/or other methods to ensure that a seal iscreated between the coronary artery CA and the wall of the heart wallMYO, to prevent hemorrhaging and to prevent the threat of or actualconduit migration. When positioning and securing of the conduit 12 iscompleted, the remaining catheter assembly is removed, leaving theconduit 12 with the vein graft therein, in place in the body

The present vascular conduit having a blood vessel graft incorporatedtherein provides significant improvements in the present treatment ofblockages or stenoses in the coronary artery. Although the invention hasbeen described in its preferred embodiments in connection with theparticular figures, it is not intended that this description should belimited in any way by the foregoing.

1-34. (canceled)
 35. A conduit for implantation in a body, the conduit comprising: an expandable, vascularly deliverable, hollow rigid tube having an interior and an exterior and configured to be positioned between and extending into at least one of a blood vessel and a heart chamber; and a section of tissue positioned within said interior of the tube between respective first and second ends of the tube, and configured to allow blood to flow therethrough, wherein the section of tissue includes at least one valve operable to restrict flow through the conduit from the blood vessel to the heart chamber during diastole. 